Coming from a similar line as you, though not 'director level', with not as much working experience as you.
I really don't see what crisis there is, maybe with your own personal matters, but with what you've told us, here goes. You've lost interest, you want to move on. 31 and already sick with office politics. You recognize people out there that are better than you, yet you also despise your "stupid colleagues". Why not improve yourself then? 4k and it's low for 31, you make do with what you can, some people 50-odd still earning 2k+, or less, some even barely getting by.
You complain about your boss, your workplace and your colleagues, yet you consider starting a company, really?
My suggestion is you harden the f*** up, and continue with the job, because the pay is good, and all that drama mama can be found everywhere, in any field. (Property, insurance, is imo much more difficult than what you have now, it's cutthroat and it's way more competitive, you will be eaten up with this attitude)
Either that, or like you said, you're drained. You have savings. Take a break then, if you think you're good enough or at least, not the worst, then obviously you can get a similar job elsewhere. During this said break, think thoroughly, what the hell you want in life. You've wasted 7-8 years, rather, invested that much into this industry, which you now have in terms of experience and knowledge. You want to jump ship to other industries and lose that? Then what, another 7-8 years time you come back and say mid-life crisis again, want to change field, don't like this don't like that, pay not good enough for 39 year old?
You got into this line knowing what to expect (I hope), if not, just get out of this industry altogether, there are alot of people who want that position, at a lower pay and who want to actually cope with all that crap.
Kopi's said everything else, you should heed his advice.